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<td width="885"> <font face="Verdana, Arial, Helvetica, sans-serif"><b><font size="6">The
Token Type</font></b></font></td>
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<blockquote>
<p><a href="class_reference_tokentype.html#introduction">Introduction</a><br>
<a href="class_reference_tokentype.html#header_synopsis">Header 'wave/context.hpp'
synopsis</a><br>
<a href="class_reference_tokentype.html#template_parameters">Template parameters</a><br>
<a href="class_reference_tokentype.html#member_functions">Member functions</a></p>
</blockquote>
<h2><a name="Introduction"></a>Introduction</h2>
<p>The token type in <tt>Wave</tt> is the main carrier of information. It is returned
by dereferencing the main iterator. The tokens are originally generated by the
lexer ("An entity that lexically transforms the subject of parsing to a
sequence of objects (called tokens) more suitable for subsequent parsing.").
The Wave library contains two different, interchangable C++ lexers, which may
be used as a starting point during developing your own application. The lexer
generated tokens are transformed by the preprocessing engine (macro expansion,
include file processing etc.) and after this returned to the user of the <tt>Wave</tt>
library.</p>
<p>You can use arbitrary token types in conjunction with your own lexer as long
as these implement some required interface. The required token type interface
is described below and is implemented by the <tt>wave::cpplexer::lex_token</tt>
template, the required lexer interface is described <a href="class_reference_lexer.html">here</a>.
</p>
<p>In the following is described the token type predefined inside the <tt>Wave</tt>
library, which is used in conjunction with the two predefined C++ lexers contained
in the <tt>Wave</tt> library too. If you need to use your own token type, it
is required to implement the interafce described below.</p>
<h2><b><a name="header_synopsis"></a>Header <a href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/spirit/spirit/wave/wave/cpplexer/cpp_lex_token.hpp?rev=HEAD&content-type=text/vnd.viewcvs-markup">wave/cpplexer/cpp_lex_token.hpp</a>
synopsis</b></h2>
<pre><span class="keyword"><code>namespace</code></span><code> wave {
<span class="keyword">namespace</span> cpplexer {
<span class="keyword">template</span> <<span class="keyword">typename</span> PositionT>
<span class="keyword">class</span> lex_token
{
<span class="keyword">public</span>:
<span class="keyword">typedef</span> <span class="keyword">std::basic_string</span><char> string_t;
<span class="keyword">typedef</span> PositionT position_t;
<a href="class_reference_tokentype.html#constructor">lex_token</a>();
<a href="class_reference_tokentype.html#constructor">lex_token</a>(token_id id, string_t <span class="keyword">const</span> &value,
PositionT <span class="keyword">const</span> &pos);
// accessors
<a href="class_reference_tokentype.html#operator_tokenid">operator token_id</a>() <span class="keyword">const</span>;
string_t const &<a href="class_reference_tokentype.html#get_value">get_value</a>() <span class="keyword">const</span>;
position_t const &<a href="class_reference_tokentype.html#get_position">get_position</a>() <span class="keyword">const</span>;
void <a href="class_reference_tokentype.html#set_token_id">set_token_id</a> (token_id id);
void <a href="class_reference_tokentype.html#set_value">set_value</a> (string_t <span class="keyword">const</span> &newval);
void <a href="class_reference_tokentype.html#set_position">set_position</a> (position_t <span class="keyword">const</span> &pos);
};
} <span class="comment">// namespace cpplexer</span>
} <span class="comment">// namespace wave</span>
</code></pre>
<h2><b><a name="template_parameters" id="template_parameters"></a>Template parameters</b></h2>
<p>The predefined token type uses a template parameter <tt>PositionT</tt>, which
allows to specify the type to be used to carry the file position information
contained inside the generated tokens. This type should contain at least the
filename, the line number and the column number of the position, where the token
was recognized. It defaults to a simple file_position template class described
<a href="class_reference_fileposition.html">here</a>. </p>
<h2><b><a name="member_functions"></a>Member functions</b></h2>
<p><b><a name="constructor" id="constructor"></a>Constructors</b></p>
<pre> lex_token();
lex_token(token_id id,
string_t <span class="keyword">const</span> &value,
PositionT <span class="keyword">const</span> &pos);</pre>
<blockquote>
<p>The first (default) constructor is for generating an end of stream token,
which is used for indicating the end of the underlying input stream.</p>
<p>The second constructor initializes the newly created token object with its
token id (for a list of valid token id's please look <a href="token_ids.html">here</a>),
the string representation of its value and the file position, describing the
position inside the input stream , where this token was recognized.</p>
</blockquote>
<h2>Accessor functions</h2>
<p><a name="operator_tokenid"></a><b>operator token_id</b></p>
<pre> <span class="keyword">operator</span> token_id() <span class="keyword">const</span>;</pre>
<blockquote>
<p>Allows the access to the token id of the token. This access function is implemented
as an implicit conversion function to allow the operation of <tt>Spirit</tt>
parsers directly on top of a token stream. The possible token id's are described
<a href="token_ids.html">here</a>. </p>
<p>This function does not throw in any case.</p>
</blockquote>
<p><a name="get_value"></a><b>get_value</b></p>
<pre> string_t <span class="keyword">const</span> &get_value() <span class="keyword">const</span>;</pre>
<blockquote>
<p>Returns the value of the token, as it was recognized in the input stream.
Even for constant tokens (as keywords or operators etc.) the returned value
reflects the character sequence as found in the input stream. </p>
<p>This function does not throw in any case.</p>
</blockquote>
<p><b><a name="get_position"></a>get_position</b></p>
<pre> PositionT <span class="keyword">const</span> &get_position() <span class="keyword">const</span>;</pre>
<blockquote>
<p>Returns the position of the token in the input stream, where it was recognized.
The position contains information about the filename, the line number and
the column number of the token. By default the <tt>Wave</tt> library uses
a file_position template for this purpose, which is described in more detail
<a href="class_reference_fileposition.html">here</a>.</p>
<p>This function does not throw in any case.</p>
</blockquote>
<p><a name="set_token_id"></a><b>set_token_id</b></p>
<pre> void set_token_id(token_id id);</pre>
<blockquote>
<p>Changes the token id of the token to the new value. The possible token id's
are described <a href="token_ids.html">here</a>. Propably this function is
of little value for the library user, but it is required under certain circumstances
for correct operation of the preprocessing engine.</p>
<p>This function does not throw in any case.</p>
</blockquote>
<p><a name="set_value"></a><b>set_value</b></p>
<pre> void set_value(string_t <span class="keyword">const</span> &newval);</pre>
<blockquote>
<p>Changes the value stored inside the token to the new value. Propably this
function is of little value for the library user, but it is required under
certain circumstances for correct operation of the preprocessing engine.</p>
</blockquote>
<p><a name="set_position"></a><b>set_position</b></p>
<pre> void set_position(PositionT <span class="keyword">const</span> &newpos);</pre>
<blockquote>
<p>Changes the position stored inside the token to the new value. This is used
for instance for implementing the functionality required for to implement
the <tt>#line</tt> directive.</p>
</blockquote>
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<hr size="1">
<p class="copyright">Copyright © 2003-2004 Hartmut Kaiser<br>
<br>
<font size="2">Use, modification and distribution is subject to the Boost Software
License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
</font> </p>
<span class="updated">Last updated:
<!-- #BeginDate format:fcAm1m -->Monday, January 5, 2004 14:57<!-- #EndDate -->
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